单项选择题
A.30 B.40 C.50 D.60
A.(0.1~0.3)d B.(0.3~0.5)d C.(0.5~0.7)d D.(0.7~0.9)d
A.1 B.1.5 C.2 D.2.5
A.1500 B.1800 C.3000 D.3600
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